Three-week-old hamsters will be inoculated intracerebrally with hamster-adapted scrapie agent in brain suspension. Control animals will be injected intracerebrally with saline brain suspension. In addition, a group of animals will be fed cuprizone. At 7-10 day intervals, animals from both groups will be killed and their eyes fixed and prepared for light microscopic and ultrastructural examination. The objectives are to 1) Characterize the pathogenesis of scrapie-related degeneration of the retina and optic nerve observed in a pilot study, and 2) Determine the ocular effects of a similar disease process to scrapie in which there is no replicating agent (cuprizone portion of the study).